Manufacture of laminated glazing

ABSTRACT

A method for manufacturing a laminated glass panel, which includes at least two glass substrates and at least one intermediate layer made of a polymeric material arranged between the substrates, the method including in the following order: the bending of the substrates; the controlled cooling of the substrates; and the formation of a laminated assembly that includes the substrates and the intermediate layer; the cutting of the laminated assembly straight through the entire thickness thereof along a line on one of the main surfaces thereof, the controlled cooling including general controlled cooling and local controlled cooling of an area that includes the cutting line, the local controlled cooling being faster than the general controlled cooling.

The invention relates to a process for manufacturing laminated glazingcomprising the cutting thereof after assembly of glass substrates withan interlayer of polymer material type. The cutting is carried outthrough the entire thickness of the laminate and may especially becarried out in order to form at least one cut-away portion such as ahole or a notch, the edges of this zone having residual compressivestresses. The cutting may also be carried out from one edge to the otherof the glazing.

During the use thereof, the glazing is subjected to thermal ormechanical stresses, in particular during the handling thereof, which itmust withstand in order to prevent the breaking thereof. For example,the windshields of a vehicle are subjected to mechanical forces at theirperiphery during the mounting thereof on a body, whether manually or viaa robot.

Besides the mechanical stresses, the glazing is subjected to stresses ofthermal origin during windshield deicing cycles.

These stresses at the edges, of thermal or mechanical origin, causerisks of breakage in particular at the edges of the glazing. In order toguarantee a good mechanical strength of the glazing, compressive edgestresses are generated during the manufacture of the glazing. These edgestresses are known and specified in the specifications of motor vehiclemanufacturers.

Besides the edges of glazing having compressive stresses, compressivestresses are also generated at the perimeter of cut-away portions.

Indeed, the cut-away portions in glazing are designed to receiveadded-on functional elements, such as for example an antenna fastenedwithin a drilling made in the thickness and at a distance from the edgeof the glazing. These cut-away portions will create two problems for theresistance to mechanical stresses: the recess creates an edge which willhave to withstand loading during use of the glazing and the recesscreates a stress concentration zone due to the local removal of material(hole, notch). In this regard, the glazing is subjected, at the edge ofits hole or notch, to various mechanical stresses which are those thatare permanent due to the attachment of the antenna, and those which aretransient occurring in particular during an impact on the antenna suchas when the vehicle passes under something low. Similarly, if, for theglazing of a tailgate, the hole is intended to receive a wiper, the edgeof the hole must withstand the closure of the tailgate.

Stresses in glass products are generated when the glass is heated at atemperature starting from which it loses its pure elastic behavior andbecomes slightly plastic, of viscoelastic liquid type. During coolingand as a function of the initial thermal inhomogeneity of the sampleand/or of the heterogeneity of the cooling itself, certain zonessolidify before others. Due to thermal expansion, permanent compressiveand tensile stresses appear within the sample during the coolingthereof. Qualitatively, the portions where the glass solidified firstcorrespond to the portions where the compressive stresses areconcentrated, whereas the portions where the glass solidified with adelay concentrate the zones of tensile stresses. The edge stressesdescribed in the present application are membrane stresses which may bedefined at any point M of the material and for a given direction as theaverage of the field stressed at this point and along this direction,the average being made in the entire thickness of the sample. At theedge of the sample, only the component of membrane stress parallel tothe edge is appropriate; the perpendicular component has a zero value.Therefore, any measurement method allowing a measurement of the averagestresses along an edge and through the thickness of the sample isrelevant. The methods for measuring edge stresses use photoelasticitytechniques. The two methods described in the ASTM standards cited belowmake it possible to measure the edge stress values:

-   -   the method using the Babinet compensator and described in the        standard ASTM C1279-2009-01, procedure B;    -   the measurements carried out with commercial apparatus such as        the Sharples model S-67 sold by the company Sharples Stress        Engineers, Preston, UK and using a Sénarmont of Jessop-Friedel        compensator. The principle of the measurement is described in        the standard ASTM F218-2005-01.

Within the context of the present application, the compressive stressvalues are determined by the method described in the standard ASTMF218-2005-01.

Generally, the compressive stress values are determined between 0.1 and2 mm from one edge and preferably between 0.5 and 1 mm from one edge.For the case where a local zone of compressive stress does not surroundan orifice insofar as it is a zone allowing for the possibility ofcreating an orifice subsequently, then the stress value can bedetermined after drilling an orifice followed by measurement of thestress at the distance from the edge of the orifice as has just beenindicated.

A known process for manufacturing laminated glazing having specificcurves for the body for which it is intended and generating compressivestresses at the edge of a cut-away portion of this glazing, consists in:

-   -   drilling, independently of one another, two flat glass sheets at        the desired location of the site of the cut-away portion;    -   grouping together the two glass sheets by superposing them (but        with no polymer interlayer at this stage), carrying out the        bending thereof by gravity at the bending temperature (the glass        being hot; it is recalled that the bending step is used to give        the curves and therefore the final three-dimensional shape to        the glazing);    -   carrying out a general controlled cooling of the whole of the        glazing generating compressive stresses;    -   placing an intermediate sheet of polymer material (generally of        polyvinyl butyral type often referred to as PVB) between the two        once more superposed sheets, performing a degassing, that is to        say eliminating the air trapped between the glass sheets and the        interlayer, and assembling them in an autoclave;    -   completing the hole by cutting the PVB at the two drillings in        the glass (alternatively, it is also possible to cut the hole in        the PVB sheet before assembly).

However, this process has certain difficulties to be overcome:

-   -   despite drillings made independently in the two respective glass        sheets according to two distinct phases, it is advisable to        ensure a good concentricity of the two drillings when the two        glass sheets are then combined;    -   the concentricity of these drillings must also be perfect during        the bending phase which precedes the controlled cooling step, if        not certain peripheral parts of each drilling are confined,        cooling more slowly, generating substantially lower compressive        stresses. However, this perfect arrangement, even more sensitive        when, in particular, the size of one of the glass sheets is in        general slightly larger than that of the other sheet for a        laminated product, depends on the deposition precision, on the        placement and maintaining of the sheets with respect to one        another on the bending tool and during the conveyance of the        glass sheets into the furnace;    -   various complications may arise during the degassing depending        on the process used; in particular, if an assembly is carried        out by calendering, the pressing of the glass sheets with the        interlayer mechanically and directly stresses the periphery of        the hole. If the latter has inhomogeneous compressive stress        zones, breakage of the glazing may occur. Another method of        degassing, consisting in drawing the vacuum between the glass        sheet and the PVB sheet (by the green snake method [peripheral        seal in which the vacuum is drawn] or the vacuum bag method) is        difficult to implement because the holes on the sheets do not        make it possible to correctly draw the vacuum;    -   the fact of bending pre-drilled glass makes optical defects in        reflection appear (slight distortion at the periphery of the        hole).

Another manufacturing process consists in carrying out a bendingoperation sheet by sheet and not simultaneously with the sheetssuperposed such as described above, eliminating the drawbacks pertainingto the latter process. However, this independent bending of the glasssheets has certain limitations such as:

-   -   the two glass sheets must be enameled at the periphery;    -   when the thicknesses or the colors are different between the two        sheets, the forming thereof is not completely identical and a        reliable and robust assembly of these two sheets becomes        difficult to carry out;    -   it is tricky to assemble complex parts, especially for glazings        with cuttings of the notched type.

Another solution has also been developed for manufacturing laminatedglazing comprising a part fastened in the adapted recess of the glazing.U.S. Pat. No. 4,124,367 thus proposes, in order to overcome the risk ofmanufacturing laminated glazing for which the recess would havecompressive edge stresses that would be lower in one of the glass sheetsrisking the breakage of the glazing during the fastening (by screwing orbonding) of a part into the recess, to only create compressive stressesat the edge of the recess for a single glass sheet, this glass sheetadditionally having an orifice with a dimension of less than that of theother associated glass sheet. Consequently, the part is fastened only toa single glass sheet, the one having a smaller orifice and that isprovided with controlled compressive edge stresses.

Nevertheless, the final product is less robust to mechanical stressessince the part is only attached to a single glass sheet.

The objective of the invention is in particular to propose a process formanufacturing laminated glazing provided, over its entire thickness,with at least one cut edge after assembly of the glass substrates as alaminate, said edge having compressive edge stresses. The cut edge mayin particular have the shape of a hole or a notch. This process issimplified with respect to existing processes for laminated glazing withholes or notches. It guarantees compressive stresses of the cut edgewith a homogeneous and sufficient intensity along this edge, for all theglass substrates assembled in the laminated glazing.

According to the invention, a cut-away portion in the laminated glazingis a hole or a notch that passes through the whole of its thickness. Ahole (or orifice) has a contour that is closed on itself entirely withinthe main faces of the laminated glazing. A notch constitutes adiscontinuity of the outer edge of the glazing in order to form aportion that is cut away toward the inside of the main faces of theglazing. It is in a way an open hole in the edge of the glazing.

The invention also makes it possible to cut laminated glazing (withoutnecessarily actually producing a hole or a notch) along a specific lineafter its assembly, as soon as the glass substrates that it containshave undergone a particular local cooling at the lines that have to becut after assembly. In this case, the cutting of the laminated assemblymay lead to several portions separated from one another, each of theseportions nevertheless having the edge stresses necessary for theirsolidity over their entire perimeter. The advantage here is of beingable to have various portions that are perfectly coincident with oneanother at their edges (cut according to the invention) and as regardstheir general shapes, the curves of one of the portions inevitablyrunning perfectly on from another portion, when the various portions arebrought together via their cut edges according to the invention.

According to the invention, the process for manufacturing laminatedglazing comprising at least two glass substrates and at least oneinterlayer made of a polymer material arranged between the substrates,the process comprising the bending of the substrates, the controlledcooling of the substrates, the assembly of the substrates and of theinterlayer, is characterized in that it comprises the following steps inthe following order:

-   -   bending of the substrates, then    -   controlled cooling of the substrates, then    -   formation of a laminated assembly comprising the substrates and        the interlayer, then    -   cutting the laminated assembly through its entire thickness        along a line (which covers the fact that the line is in several        portions if there are several holes) on one of its main faces,        the controlled cooling comprising a general controlled cooling        and a local controlled cooling of the zone comprising the        cutting line, the local controlled cooling being faster than the        general controlled cooling.

The expression “glass substrate” means: individual glass sheet which mayor may not be covered with one or more layers (such as anti-reflectionlayers, solar-control layers, anti-abrasion layers, etc.). A glass sheetcomprises two main faces; the same is true for a glass substrate. Theexpression “laminated assembly” may denote the final laminated glazingbefore the cutting thereof according to the invention when it is theglazing after cutting that is mounted on the motor vehicle.

Within the context of the present application, a difference is madebetween the following two types of coolings applied to the glasssubstrates:

-   -   a) The “general controlled cooling” which makes it possible to        generate compressive stresses on the outer edges of the        substrates in order to obtain a sufficient mechanical strength        at these edges. This cooling is applied globally to the whole of        the glazing. This type of global cooling is well known to a        person skilled in the art.    -   b) According to the invention, a “local controlled cooling” is        applied in order to generate compressive stresses that enable        the cutting in the glass after bending and that furthermore        cause the presence of compressive stresses on the edges of the        line which will then be cut. This local controlled cooling is        faster than the general cooling.

Thus, the process of the invention provides several advantages withrespect to the prior art processes, in particular:

-   -   it limits the cutting (or drilling) to a single step after        formation of the laminated assembly, through the entire        thickness of the laminated assembly comprising the two glass        substrates and the interlayer, instead of two cutting operations        before bending for each of the glass substrates, and a finishing        operation in order to remove the interlayer portion between the        two cut portions of the substrate;    -   the problem of the relative positioning of the two glass        substrates during bending is avoided;    -   the presence of a hole during the assembly makes the degassing        operation complex, drilling after assembly simplifies the        degassing operation;    -   the optical quality is improved, in particular for the optical        distortions in reflection in the vicinity of the cut zone.

Moreover, the process makes it possible to produce compressive stresseson the edges created by the cutting according to the invention for eachof the two assembled glass substrates. Thus, any part to be fastened ina recess produced according to the invention may be fastened to the twoassembled glass substrates and not to only one as in the prior art,guaranteeing a better fastening strength.

According to one feature, the local controlled cooling constitutes aninhomogeneous cooling of the main faces. If the local controlled coolingis applied to the glass substrates separately (glass substrates notside-by-side), it may be applied to only one or both main surfaces ofeach glass substrate. If the local controlled cooling is applied to astack of glass substrates (which are therefore side-by-side), then thelocal controlled cooling may be applied to only one or both mainsurfaces of the stack.

The local controlled cooling of the zone comprising the line intended tobe cut is faster than the general controlled cooling of said substrates.The local cooling is applied at the line to be cut subsequently. Thislocal cooling zone covers the entire cutting line generally from atleast 1 mm on either side of this line. In certain cases, the localcooling may also be widened to a neighboring zone which will be removedfrom the laminated assembly but which will not necessarily be directlysubjected to the cutting tool. By way of example, if it is desired toproduce a hole having a diameter of a few centimeters in the laminatedassembly, the local cooling can be carried out over the entire surfacecorresponding to the hole (in fact in a manner slightly more spread outthan the hole), whereas the cutting will only be applied around thecontour of the hole. In the case of a hole having a relatively largedimension (the case of cutting the orifice corresponding to the openingof an opening sunroof), it is preferable to apply the local controlledcooling only to the line intended to be cut. Indeed, it is pointless toapply this local controlled cooling to the entire surface intended to becut away if the latter is large. The method of local cooling followingthe contour of the zone to be cut is preferred when the smallestdimension of the zone undergoing the local controlled cooling has adimension of greater than 80 mm in the main face of the glazing. Itremains possible for smaller dimensions. When a recess exceeds a widthof 80 mm at any one of its points, it is preferable to apply the localcooling to the contour of the recess (and not to the entire surface ofthe recess).

The local controlled cooling is obtained by convection, conduction,radiation, or a combination of these means.

Generally, the local controlled cooling is applied between the start andthe end of the general cooling. However, beginning the local coolingtoward the end of the bending operation when the general cooling has notbegun is not ruled out. Thus, the local controlled cooling is generallyapplied in a cooling chamber preferably at the start of the generalcooling of the glazing in the cooling chamber. As a variant, it may bestarted at the end of the bending chamber.

A controlled cooling chamber applies the general controlled cooling. Ifthe local controlled cooling is also applied therein, this chamber isfurthermore equipped with means necessary for the application of thislocal controlled cooling. These means may, for example, be a nozzle thatlocally blows onto one of the faces of the superposed sheets. It mayalso be a cold metal component (cooled internally by air for example)that comes into contact with the local zone to be cooled more rapidly.

Advantageously, the bending and the cooling are both carried out on thetwo glass substrates arranged side-by-side (that is to say which arejuxtaposed, in particular superposed, without any means of adhesionbetween the substrates). In particular, the two side-by-side substratesmay move into at least one bending chamber then into at least onecontrolled cooling chamber, the localized controlled cooling possiblybeginning in the last bending chamber or in a controlled coolingchamber.

The bending of side-by-side glass substrates is carried out with noorganic material between them considering the temperature needed for thethermal bending. The thermal bending is carried out before assembly withthe interlayer of polymer material since the latter begins to degradefrom 160° C. with formation of bubbles. If it were cooled from such alow temperature, it would furthermore be impossible to generatepermanent compressive edge stresses in the glass.

The bending of glass substrates may especially be carried out bypressing and/or suction at the bending temperature, as taught by WO02/064519, WO 2006/072721 and WO 2004/087590. This bending is carriedout on the glass substrates having to then be assembled, in aside-by-side manner. In particular, the two side-by-side glasssubstrates may move into chambers for pre-bending via gravity, then intoa pressing and/or suction chamber and finally into controlled coolingchambers, the local controlled cooling optionally beginning at the endof the pressing or in the cooling chambers. The whole of the controlledcooling, which begins at a temperature above 580° C. (generally between650 and 580° C.), is carried out in the cooling chambers, optionallybeginning first in the last bending chamber, at least until thetemperature drops to 520° C., or even below this temperature.

The (general and local) controlled cooling is applied when thesuperposed glass sheets have just been bent at their bendingtemperature. The entire cooling process is generally carried outdirectly starting from the bending temperature. Outside of the zonesthat are undergoing the local controlled cooling, the temperature of theglass generally drops from the bending temperature to ambienttemperature without ever going back up (monotonic temperature drop).

The fact of simultaneously bending, in the side-by-side state, the twosheets intended to be assembled has the advantage that the various glasssubstrates may be of optionally different thickness and color. Indeed,the two substrates will certainly take on the same curvatures despitetheir differences.

The bending of the glass substrates may also be carried out by pressingand/or suction applied to the glass substrates individually (“sheet bysheet”).

The bending is not necessarily applied in a chamber, it being possiblefor the bending tools to be in the open air.

Similarly, the general and local controlled coolings are not necessarilyapplied in a chamber.

Preferably, the start of the general controlled cooling is controlledbetween 0.3 and 8° C./second, and more preferably between 0.3 and 2°C./second until the temperature of the glass (between 650 and 580° C. onleaving the bending operation) reaches at least 520° C.

For the case where the glass substrates are side-by-side before thelocal cooling, the local controlled cooling is applied from a singleside opposite one of the faces of the two side-by-side glass substrates,or else from two opposite sides of the two side-by-side glass substratesthat are facing each other. If the local controlled cooling is appliedagainst the surface of a single glass substrate, it produces its effectsthroughout the thickness of the two side-by-side glass substrates,insofar as the thickness of the side-by-side substrates is not toolarge, of course, and the local cooling is of sufficient duration andintensity. The local controlled cooling may be applied from a singleside of the stack of substrates subject to guaranteeing a localcontrolled cooling that is faster, throughout the thickness, than thegeneral controlled cooling. It may also be applied from both sides, andthe coolings applied on each side must be in this case facing eachother.

The local controlled cooling is sufficient in duration and in intensityso that the edge stresses after cutting of the laminated assembly aregreater than 4 MPa and preferably greater than 8 MPa. Routine testsreadily enable this adjustment.

The general controlled cooling of the glazing may, as is known, use heattransfer such as convection, radiation, conduction or a combination ofthese three heat transfer methods.

In the present application, the zone having undergone the localcontrolled cooling may be referred to as the “compressive zone” or“compression zone”.

The differentiated and localized cooling of the glass substrates inorder to obtain compression zones may be carried out by any means, forexample by convection, or radiation, or else conduction, or even acombination of these means. This local differentiated cooling consistsin cooling more rapidly over the line intended to be cut after assemblyof the glass substrates than the rest of the glazing.

Convection consists in blowing cold air (air at ambient temperature)aimed at the zones that it is desired to put under compression.Depending on the average cooling rate of the glazing, the temperature ofthe injected air and/or the intensity of the blowing will be adjusted.

Conduction aims to bring the portions of the glass that it is desired tocool more rapidly into contact with a material that is colder than thesurface of the glass.

Regarding radiation, it is possible to use a colder material that isplaced opposite the glass. The heat exchange via radiation will enable agreater local cooling of the zone facing the material.

According to another example, masks are used that limit the cooling rateoutside of the zones where it is desired to establish compressivestresses. Zones are thus created outside of the masks that correspond tothe compression zones, for which the cooling of the glass is greater.

An example of a mask is an insulating material, in particular fibrousmaterial, having a surface area equivalent to that of the glazing and inwhich openings are made. The material is placed close to the hot glassduring its cooling phase. Placed in a cold atmosphere, the portions ofthe glazing that are opposite the openings cool more rapidly than thosewhich are masked.

It is consequently possible to use coating materials that increase ordecrease the emissivity of the glass at the surface.

It is possible to use a coating with greater emissivity than the surfaceof the glass and to put it against the desired compression zones; thesezones will then cool more quickly.

Conversely to the example above, it is possible to use a coating withlower emissivity than the surface of the glass and to put it against thesurface of the glass outside of the desired compression zones; thesezones will then cool more slowly than the zones to be put undercompression.

As materials that increase or decrease the emissivity of the glass atthe surface, it is possible to use materials that enable the surface ofthe glass to be easily coated. In this case, they are preferablynon-toxic, temperature-resistant and are readily dispersible or solublein water.

The start of the general cooling is preferably controlled between 0.3and 2° C. per second from the end of bending temperature, between 580°C. and 650° C., on leaving the bending operation until the temperatureof the glass reaches 520° C., or even lower.

Below 520° C., it is possible to apply a convective cooling of the wholeof the glazing in order to accelerate the process. Below 480° C., it ispointless to continue applying the local controlled cooling, since thewhole of the glazing can then undergo the same general cooling. Theglass leaves an optional cooling chamber in general at less than 300° C.

By way of example, the local controlled cooling is applied by means ofan air-blowing nozzle, one end of which has a cross section of suitableshape in order to blow onto the line to be cut, and is affixed againstat least one of the glass substrates at the line to be cut. For example,if the line to be cut has the shape of a circle, the orifice of thenozzle may have the shape of a disk or a ring. In the case of a disk,the diameter of the disk is slightly greater than that of the circle tobe cut and it is the entire surface within the circle that will undergothe local controlled cooling. In the case of a ring-shaped nozzle, thenozzle blows over a ring-shaped zone on the circle and not inside thisring.

As a variant or in combination, the local controlled cooling is obtainedby application, against or in the vicinity of the surface of the glass,of a temporary coating material in particular of fabric type thatincreases or decreases the thermal radiation toward or emitted by theglass, and that is provided with at least one opening, this openingcorresponding to the zone comprising the cutting line or else to theremaining portion of the glazing (zone not comprising the cutting line)depending on the type of material. In this case, the differentiatedcooling (local cooling more intense over the line to be cut than thegeneral cooling next to the line to be cut) is obtained here by actingon the difference in thermal radiation emitted by the glass as aconsequence of the application of the temporary coating material.

As a variant or in combination, the local controlled cooling is obtainedby application, against the surface of the glass, of a contact materialat a temperature below that of the glass, the zones in contactcomprising the line to be cut. It may be a component made of cold metalsuch as steel covered with a metallic fabric in order to prevent thermalshocks. A coolant (air or water) may run through this cold metalcomponent in order to keep it cold. The differentiated cooling (localcooling faster than the general cooling next to the zone to be cut) isobtained here by acting on the difference in heat transfer by conductionemitted by the glass as a consequence of the application of the contactmaterial.

The process of the invention in particular provides laminated glazingfor which the dimension of the cut is adapted to the particular use ofthe glazing.

According to the invention, the cut edge may be intended to receive afunctional part (such as an antenna, a brake light, a camera, etc.)fastened to the two assembled glass substrates, or may act as a simplepassage for shafts or cables, and/or constitutes the open portion of anopening sunroof.

The invention also relates to laminated glazing comprising at least twoglass substrates and at least one interlayer made of a polymer materialarranged between the substrates, and at least one cut-away portion(orifice or notch) in its thickness, characterized in that the cutcontours of the two glass substrates in the cut-away portion have aperfect superposition, and in that the compressive edge stresses ofthese contours are greater than 4 MPa, preferably greater than 8 MPa.The compressive edge stresses are generally less than 20 MPa.

The laminated glazing may be shaped at the edge of the cut, for examplechamfered on at least one of the substrates, or on both substrates.

As an application example, the laminated glazing may be a rear window ofa motor vehicle, it being possible for the cut material to constitute anorifice (cut-away portion) for the passage of an equipment componentsuch as a wiper shaft. The contour of the orifice has compressive edgestresses in accordance with the invention.

As another application example, the laminated glazing constitutes anopening sunroof, it being possible for the cut material to constitute acut-away portion forming the opening of the roof. According to thisembodiment, the cut constituted an orifice entirely within the mainfaces of the laminated glazing. According to another example, theinvention enables the production of a vehicle roof, the laminatedglazing constituting an opening sunroof, cut into at least two portionsafter assembly as a laminate, said portions being perfectly coincidentat the location where the cutting according to the invention was made.Such a type of roof may therefore be opened by moving one of the roofportions, or even moving several roof portions. The type of cuttingaccording to the invention suitable for this type of application isrepresented in FIG. 3 f. Thus, the invention also relates to a processfor manufacturing an opening sunroof of a vehicle, comprising theprocess of preparing laminated and cut glazing according to theinvention, the cutting producing two portions, each portion comprisingan edge, the contour of which coincides with an edge of the otherportion, said two edges having been produced by cutting, the twoportions being mounted as an opening sunroof of a vehicle with the aidof fastening and guiding means, it being possible for the two portionsto move closer together or move apart in accordance with the guidingmeans in order to close said roof by juxtaposition of the two edges orin order to open said roof by separating the two edges. A single one ofthese laminated glazing portions may be movably mounted on the vehicleor the two portions may be movably mounted on the vehicle. The fasteningmeans are those connecting the glazing in two portions to the vehicle.The guiding means are those that impose the movement of one or bothportions during the opening or closing of the opening sunroof. Themovement may be a lifting followed by a translation or a rotation or anyother movement that makes it possible to open and reclose the roof bymoving one or both portions of the laminated glazing. The edges of theportions that are moved apart or closer together during the opening orclosing of the roof are those which were created during the cutting andthis is why they coincide perfectly. Of course, on closing the roof, theedges are brought together with the same direction as they were createdduring the cutting.

The cutting step is obtained by known cutting means such as a diamondhole saw, a diamond router or a water jet.

Depending on the cutting means chosen, it is possible to cut thelaminated assembly from a single one of its main faces or from both ofits sides at once via one of the following means:

-   -   hole saw or router: preferably the two main faces are cut at the        same time,    -   water jet: a single side is sufficient.

The number of operations in the process for manufacturing laminatedglazing according to the invention is reduced compared to the knownprocesses for cutting before bending. Furthermore, obtaining a perfectcontinuity of the edges of the cut along the two glass substrates and inthe thickness of the assembled glazing is ensured.

Finally, this manufacturing process finds all its advantages in theparticular application according to which the laminated glazingconstitutes an opening sunroof. Indeed, a saving of material is achievedbecause the cut portion corresponding to the material of the recess ofthe glazing can be recovered in order to manufacture the opening of theroof. Furthermore, perfect geometric continuity is ensured between theroof around the opening and the opening, which is currently difficult toachieve by standard processes when the two glazings (on the one hand theroof comprising an orifice fastened to the vehicle and on the other handthe moving portion that conceals this orifice) are formed by twoindependent manufacturing processes.

The invention also makes it possible to produce laminated glazingscomprising at least one local compressive zone that permits the cutting.It is thus possible to market laminated glazing of this type, which isnot cut but that comprises a compressive zone that permits the cutting,it being up to the client to carry it out or not. It is thereforepossible, for example, to mount such uncut but cuttable glazing as amotor vehicle roof. The owner of the vehicle can then decide, or not, tocarry out the cutting in order to form an opening sunroof on hisvehicle. Of course, the location of the compressive zone is dulyidentified by the manufacturer so that the location of the cutting isclearly established. Laminated glazing comprising at least one localzone of compressive stresses within its main faces is also the subjectof the invention as an intermediate product. This local zone ofcompressive stresses is different from the compressive stresses of theouter edges of the glazing forming a peripheral border of compressivestresses. The local zone of compressive stresses is within this borderof compressive edge stresses. The local zone may however join the borderof compressive edge stresses. Thus, the invention also relates tolaminated glazing comprising at least two glass substrates and locallycomprising, in each of the glass substrates and facing each other in allthe glass substrates (the compression zones are placed at the samelocation, that is to say superposed from one glass substrate to the nextin the laminated glazing), a zone comprising compressive stressesenabling the cutting of said glazing along a line included in said zonein order to form, after cutting, edges having compressive edge stressesof greater than 4 MPa, preferably of greater than 8 MPa. Generally, thecompressive edge stresses after cutting are less than 20 MPa. Theglazing can therefore be manufactured free of orifices in the local zoneof compressive stresses. The cutting in this zone is carried outsubsequently on the instructions of the vehicle owner and may be used,for example, to develop an opening sunroof or orifices for fasteningroof bars. Thus, the invention also relates to a vehicle roof (generallya motor vehicle roof) comprising laminated glazing comprisingcompressive stresses that make it possible to drill orifices in thelaminated glazing after mounting on the vehicle.

The compressive edge stresses in the peripheral border are generallybetween 4 and 20 MPa. The border of compressive edge stresses generallyhas a width on each main face of the glazing of 0.1 to 3 cm countingfrom the outer edge.

The laminated glazing “to be cut” according to the invention isgenerally symmetrical with respect to a longitudinal median planepassing through the middle of its front transverse strip and the middleof its rear transverse strip (the “longitudinal” direction correspondingto the direction of travel of the vehicle, the “transverse” directionbeing perpendicular to it). This plane also passes through itsbarycenter. The laminated glazing according to the invention maycomprise at least two local zones of compressive stresses enabling,after drilling of orifices within said zones, the fastening of a roofbar, fastening components of said bar passing through said orifices.These zones of compressive stresses are generally placed symmetricallywith respect to the plane of symmetry of the glazing (longitudinalmedian plane) passing through the middle of the front transverse stripand the middle of the rear transverse strip of the glazing. Thelaminated glazing according to the invention for the application as avehicle roof with the possibility of fastening roof bars comprises two,four or six local zones of compressive stresses enabling, after drillingorifices in said zones, the passage of fastening components of two roofbars. For this application, each zone of compressive stresses generallyhas an area between 0.5 cm² and 70 cm². Each zone of compressivestresses is generally at less than 30 cm and more generally less than 20cm from a longitudinal edge of the laminated glazing serving as theroof.

The present invention is now described with the aid of purelyillustrative examples that in no way limit the scope of the invention,and using the appended illustrations, in which:

FIG. 1 represents a partial schematic cross-sectional view of laminatedglazing obtained according to the process of the invention;

FIG. 2 is a variant of FIG. 1;

FIGS. 3 a to 3 i are various exemplary embodiments of geometric shapesof localized controlled cooling;

FIG. 4 is a schematic partial cross-sectional view of a device for localcontrolled cooling by blowing applied to the surface of the glass;

FIG. 5 represents a motor vehicle roof panel comprising laminatedglazing according to the invention in two portions acting as an openingsunroof, one portion of said glazing being fixed, the other beingmobile;

FIG. 6 illustrates laminated glazing comprising orifices or zones ofcompressive stresses enabling the drilling of orifices;

FIG. 7 is a schematic partial cross-sectional view of a local controlledcooling device that comes into contact with the surface of the glass;

FIG. 8 represents a motor vehicle roof seen perpendicular to one of itsmain faces and comprising a border of compression and four local zonesof compressive stress joining the border, said local zones being readyto receive orifices.

FIG. 1 illustrates a partial cross-sectional view of laminated glazing 1comprising at least, depending on its thickness, one cut-away portion 2.The glazing comprises at least two glass sheets or substrates 10 and 12,and an interlayer or intermediate sheet 11 made of polymer materialarranged between said glass substrates. After manufacture, the glazinghas the cut-away portion 2 obtained by drilling of the two glasssubstrates and of the interlayer, after the assembly thereof. Theorifice obtained in the first substrate has a contour 20 while the otherorifice in the second substrate has a contour 21. According to themanufacturing process of the invention:

-   -   The two contours 20 and 21 are perfectly superposed; according        to the cross-sectional view, the edges of the substrates over        the entire periphery of the contours are perfectly aligned; of        course, if the drilling is carried out simultaneously from the        two main faces of the glazing, it is advisable to ensure the        alignment of the drilling tools on either side of the glazing.        In particular, water-jet cutting can be carried out from a        single side of the laminated glazing.    -   The contours 20 and 21 both have compressive edge stresses of        greater than 4 MPa, and preferably of greater than 8 MPa.

The orifices of the substrates may be shaped depending on theapplication. For example, FIG. 2 shows the recess 2 with chamfers 23 and24 on each of the outer edges of the two contours 25 and 26. The recess2 has dimensions adapted to the application that is made thereof. Thisrecess is used, for example, to fasten a functional or aesthetic partsuch as an antenna, a fan, a trim, or is used as a passage for a cable,etc. If it is of large dimensions, this recess may constitute theopening of a glass opening sunroof for a vehicle, in particular for amotor vehicle.

The process for manufacturing the glazing comprises various steps whichwill be successively described. The individual glass substrates 10 and12 are first cut along their outer edges by a standard method forcutting glass in order to provide substrates having the desired externalperipheral shapes, according to the cutting of primitives, the cuttingto shape, the break-out thereof and the optional shaping thereof. One ormore optional additional steps of screen printing may be carried out,depending on the application. On the production line, many substratesare thus prepared on the run. Then, with the substrates running on theproduction line, a step of pairing is carried out. The substrates 10 and12 are combined together by superposition. The superposed substrates arethen bent together to the desired shape by the chosen bending process.The superposition of the glass substrates for this bending step makes itpossible to obtain glasses having perfectly coincident general shapes.According to the invention, a step of general and local controlledcooling is then carried out. The local cooling is generated on at leastone zone of a peripheral face of the side-by-side substratescorresponding at least to the zone which will be cut at the end of theprocess. The objective of the local controlled cooling is to obtaincompression zones in the thickness of the glazing at the cut edges.

The localization of the cooling in the zones intended to be cut targetsboth surfaces and contours. The localized cooling may in particular becarried out along a simple line crossing the glazing from one edge toanother edge, or even from one edge to the same edge. FIGS. 3 a to 3 iillustrate nonlimiting exemplary embodiments of local controlledcoolings over zones with various shapes.

FIG. 3 a presents a local compression zone in the form of a closedcircular contour and having a surface (hatched surface) delimited bythis circle, making it possible for example to obtain the glazing fromFIG. 1.

FIG. 3 b shows several local surface compressive zones that areindependent of one another.

FIG. 3 c illustrates a local compression zone that is in the form of asingle closed contour, the interior of the contour not being part ofsaid zone.

FIG. 3 d shows a local compression zone in the form of a curved linereaching the edge of the glazing at only one of its ends.

FIG. 3 e illustrates a local compression zone in the form of a closedloop and having a curved line going from this loop to the edge of theglazing.

FIG. 3 f shows a local compression zone in the shape of a curved linestarting from one edge of the glazing and reaching the opposite edge(the line could also return to an edge adjacent to the starting edge).

It is also possible to connect independent local compression zones usingone or more lines that may or may not reach the edge of the glazing, asillustrated in FIG. 3 g.

FIGS. 3 h and 3 i show a compression surface beginning from one edge ofthe glazing forming a specific notch and reaching the same edge of theglazing.

FIG. 4 illustrates a schematic device 3 suitable for blowing onto one ofthe sides of the side-by-side substrates. Here, air is blown at ambienttemperature over a disk-shaped area as shown by FIG. 3 a, with a view tosubsequently producing the recess from FIGS. 1 and 2. The blowing timeis between 40 and 90 seconds approximately. The blowing duration isindependent of the surface area to be cooled in a differentiated mannerbut, on the other hand, depends on the thickness of the glass. The 40seconds of local cooling are established for substrates each having athickness of 2.1 mm. The blowing nozzle has an ending with a shapeadapted to the geometric shape of the local zone of compressive stressesto be obtained. It may in particular have the shape of a rectangularcontour for a recess of relatively large dimension such as thattargeting an opening sunroof application. In FIG. 4, the nozzle 3comprises a central air supply duct 30, an axially symmetric duct 31,around the central supply duct 30. The duct 31 opens, as ending of thenozzle, into a cylindrical bell 33, the wall of which is constituted ofa flexible felt based on metal fibers. The free end 34 of the bell isput against the surface of the glass. Cold air is conveyed via thesupply duct 30 to the bell 34 in order to be released against thesurface of the glass to be cooled then discharged via the duct 31. Afterthe cooling, the de-pairing (the dissociation) of the two substrates 10and 12 is carried out. Then, the steps of assembling with the interlayer12, of degassing the assembly and of passing into an autoclave arecarried out in the standard manner. This treatment leads to bondingbetween the interlayer and the glass substrates on each side of theinterlayer. Finally, the cutting of the glazing is carried out over thezone that has undergone local cooling in order to obtain the desiredcut-away portion or portions (by diamond hole saw, diamond router, waterjets, etc.).

FIG. 5 illustrates a motor vehicle roof 40 comprising laminated glazingaccording to the invention that acts as an opening sunroof, said glazingbeing in two portions 41 and 42, one portion 41 of said glazing beingfixed with respect to the vehicle, the other portion 42 being mobile. InFIG. 5 a), the roof is closed. In FIG. 5 b), the roof is open owing tothe movement of the portion 42 only (arrow) which comes above the bodyenclosed in the roof panel of the vehicle. According to the invention,firstly a single laminated glazing was manufactured initially comprisingthe two portions 41 and 42 not yet cut. According to the invention, alocal zone of compressive stresses was created at the location wherethis glazing was to be cut in a line crossing it completely (line havinggiven rise to the edges 44 and 45 after cutting). The cutting accordingto the invention was carried out on this line and led to the portions 41and 42 that are completely independent but for which the edges 44 and 45are perfectly coincident when the roof is closed (FIG. 5 a)).

FIG. 6 represents glazing 1 made of laminated glass. The four hatcheddisks 2 represent either orifices or local zones of compressive stressesenabling the drilling of orifices. These orifices or local zones ofcompressive stresses are here completely within a main face 3 of theglazing without sticking out over the outer edge of the glazing (as isthe case for a notch). The orifices are placed symmetrically withrespect to the plane of symmetry 4 passing through the middle 5 of thefront strip 6 and the middle 7 of the rear strip 8 of the panel 1.

FIG. 7 illustrates a schematic device 70 suitable for cooling, viaconduction, a local zone through a main face of a stack of twoside-by-side substrates 73 and 74. A metal pipe 71, closed at its lowerend, has cold air running through it as indicated by the arrows. Thecontact with the glass between the metal pipe and the glass is softenedowing to a felt 72 made of refractory fibers in order to reduce the riskof breakage by thermal shock. This thus results in the formation of alocal zone of compressive stresses at the location of the contactbetween the felt 72 and the glass.

FIG. 8 represents a motor vehicle roof comprising laminated glazing,seen perpendicular to one of the main faces 81. This laminated glazingcomprises two transverse edges 87 and 88 and two longitudinal edges 89and 90. It comprises a border 82 of compressive edge stresses goingcompletely around the glazing. The longitudinal median plane AA′(perpendicular to the figure) is a plane of symmetry of the glazing andis perpendicular to the transverse edges 87 and 88 which are oppositeone another. Within the border of compressive edge stresses are fourlocal zones of compressive stresses 83, 84, 85, 86. These local zoneshere meet the border. These compression zones are represented byhatching but in reality they are not visible to the naked eye. The localzones 83 and 84 are placed symmetrically one opposite the other withrespect to the plane of symmetry AA′. The local zones 85 and 86 areplaced symmetrically opposite one another with respect to the plane ofsymmetry AA′. These local zones offer the possibility of drillingorifices through the laminated glazing for the passage of roof barfastening components. Two roof bars may be fastened, either parallel tothe plane of symmetry AA′ between the points 83 and 85 for one andbetween the points 84 and 86 for the other, or perpendicular to theplane of symmetry AA′, between the points 83 and 84 for one and betweenthe points 85 and 86 for the other.

1.-22. (canceled)
 23. A process for manufacturing laminated glazingcomprising at least two glass substrates and at least one interlayermade of a polymer material arranged between the substrates, the processcomprising in the following order: bending the substrates; controlledcooling the substrates; forming a laminated assembly comprising thesubstrates and the at least one interlayer, and cutting the laminatedassembly through its entire thickness along a cutting line on one of itsmain faces, the controlled cooling comprising a general controlledcooling and a local controlled cooling of a zone comprising the cuttingline, the local controlled cooling being faster than the generalcontrolled cooling.
 24. The process as claimed in claim 23, wherein thelocal controlled cooling is obtained by convection, conduction,radiation, or a combination thereof.
 25. The process as claimed in claim23, wherein the bending and the general and local coolings are carriedout on the two glass substrates arranged side-by-side.
 26. The processas claimed in claim 23, wherein the local controlled cooling is appliedfrom a single side opposite one of the faces of the two side-by-sideglass substrates.
 27. The process as claimed in claim 23, wherein thelocal controlled cooling is applied from two opposite sides of the twoside-by-side glass substrates that are facing each other.
 28. Theprocess as claimed in claim 25, wherein the two side-by-side substratesmove into at least one bending chamber, and into at least one coolingchamber, the localized controlled cooling beginning in a bending chamberor a cooling chamber.
 29. The process as claimed in claim 23, whereinthe bending is carried out between 580 and 650° C. and wherein a startof the general cooling is controlled between 0.3 and 8° C./second atleast until the temperature of the glass reaches 520° C.
 30. The processas claimed in claim 29, wherein the start of the general cooling iscontrolled between 0.3 and 2° C./second.
 31. The process as claimed inclaim 23, wherein the local controlled cooling is applied by blowing airby means of a nozzle, one end of which has a cross section of shapecorresponding to the zone comprising the cutting line.
 32. The processas claimed in claim 23, wherein the local controlled cooling is appliedby means of a material with the shape corresponding to the shape of thezone comprising the cutting line, said material having a temperaturelower than that of the glass, said material being brought into contactwith at least one of the glass substrates at said zone.
 33. The processas claimed in claim 23, wherein the local controlled cooling is appliedby means of a material with the shape corresponding to the shape of thezone comprising the cutting line, said material having a temperaturelower than that of the glass, said material being brought opposite butnot in contact with at least one of the glass substrates at said zone.34. The process as claimed in claim 23, wherein the local controlledcooling is obtained by applying against the surface of the glass atemporary coating material, which increases or decreases the emissivityof the glass, and that is provided with at least one opening.
 35. Theprocess as claimed in claim 23, wherein the cutting is obtained by ahole saw, a router or a water jet.
 36. The process as claimed in claim23, wherein the cutting produces a hole or a notch in the completethickness of the laminated glazing.
 37. The process as claimed in claim23, wherein the local controlled cooling is sufficient in duration andin intensity so that edge stresses after cutting of the laminatedassembly are greater than 4 MPa.
 38. The process as claimed in claim 37,wherein the edge stresses are greater than 8 MPa.
 39. A process formanufacturing an opening sunroof of a vehicle, comprising: performingthe process of claim 23, the cutting producing two portions, eachportion comprising an edge, a contour of which coincides with an edge ofthe other portion, said two edges having been produced by the cutting;mounting the two portions as the opening sunroof of the vehicle with theaid of fastening and guiding means, it being possible for the twoportions to move closer together or move apart in accordance with theguiding means in order to close said roof by juxtaposition of the twoedges or in order to open said sunroof by separating the two edges. 40.A laminated glazing comprising at least one edge cut in its thicknessobtained as claimed in claim
 23. 41. A laminated glazing comprising atleast two glass substrates and at least one interlayer made of a polymermaterial arranged between the at least two substrates, and at least onenotch or orifice cut in its thickness, wherein cut contours of the twoglass substrates in the notch or orifice have a perfect superposition,and wherein compressive edge stresses of said contours are greater than4 MPa.
 42. The laminated glazing as claimed in claim 41, wherein thecompressive edge stresses are greater than 8 MPa.
 43. The laminatedglazing as claimed in claim 41, wherein the notch or orifice ischamfered or shaped on at least one of the glass substrates.
 44. Thelaminated glazing as claimed in claim 41, wherein said glazing is bent.45. An opening sunroof of a vehicle comprising a laminated glazing asclaimed in claim 41, said sunroof comprising an orifice cut in itsthickness, wherein the material cut to form the orifice constitutes theopening of said roof.
 46. An opening sunroof of a vehicle made oflaminated glazing comprising at least two portions that are moveablecloser together or moveable apart, said portions being perfectlycoincident at the edges of the portions intended to be moved closertogether and at curvatures of all of the glazing.
 47. A motor vehiclerear window comprising a laminated glazing as claimed in claim 41, saidlaminated glazing comprising an orifice for the passage of an equipmentcomponent, acontour of said orifice having compressive edge stresses.48. The motor vehicle rear window as claimed in claim 47, wherein theequipment component is a wiper shaft.
 49. A laminated glazing comprisingat least two glass substrates, comprising a border of compressive edgestresses and locally comprising in each of the at least two glasssubstrates and in a superposed manner in all the at least two glasssubstrates a local zone of compressive stresses free of orifices anddifferent from said border, enabling a cutting of said glazing along aline within said local zone in order to form, after cutting, edgeshaving compressive edge stresses of greater than 4 MPa.
 50. Thelaminated glazing as claimed in claim 49, wherein the compressive edgestresses are greater than 8 MPa.
 51. A vehicle roof comprising theglazing as claimed in claim 49.